Bed foundation

ABSTRACT

A bed foundation has a rectangular top panel and opposite side and end panels depending downwardly from the top panel to form a box-like enclosure having an open lower end, the panels being formed integrally. A support structure of raised ribs in a predetermined regular pattern is formed integrally on the lower surface of the top panel. The foundation is made entirely or substantially entirely from an expanded rigid plastic foam material with high flame retardancy.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation-In-Part of application Ser. No. 10/635,973 filed Aug. 7, 2003.

BACKGROUND OF THE INVENTION

The present invention relates to bed structures, and is particularly concerned with a bed foundation for supporting a mattress or the like.

A conventional bed or mattress support typically consists of a foundation unit or box spring unit placed on top of a metal bed frame having side rails, cross members, and legs. A typical box spring unit consists of a base having a wooden perimeter with wooden cross slats which are nailed, glued, or stapled together, metal spring units attached to the cross slats, and a suitable cover. The separate metal base frame and foundation unit are cumbersome and involve high labor costs in manufacture. Wood is also highly flammable and current construction methods are incapable of meeting new U.S. flammability standards.

Plastic bedding foundations to replace a conventional wood and metal foundation have been proposed in the past. U.S. Pat. No. 5,953,775 of Mauro et al. describes a foundation which has a top deck member, spaced side walls, and spaced end walls which may be formed integrally or separately out of plastic material by compression molding, injection molding, or thermo-forming. Patent Application Publication No. 2002/0069462 of Gaboury et al. describes a similar bed foundation made of blow-molded plastic. The foundation is made up from separate components which can be secured together to assemble the foundation. The multiple components may make assembly of the foundation relatively complex.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a new and improved bed foundation.

According to one aspect of the present invention, a bed foundation is provided, which comprises a rectangular top panel having opposite sides, opposite ends, and four corners, a pair of side panels depending downwardly from opposite sides of the top panel, and a pair of end panels depending downwardly from opposite ends of the panel to form a box-like enclosure having an open lower end, the panels being formed integrally and being of expanded rigid plastic foam material, the top panel having an upper surface and a lower surface, and a support structure formed integrally on the lower surface of the top panel, the support structure comprising raised ribs forming a predetermined regular pattern.

The support structure may comprise first and second sets of parallel ribs which intersect at an angle to one another to form a lattice. The lattice may be of square, rectangular, diamond pattern or other geometric pattern. The lattice support structure may be modified in order to provide the desired level of support for the mattress. The central ribs may be made thicker or taller to provide additional stiffness. The ribs may also be made thicker at the edges of the top panel to fulfill the desired edge support requirements. The support structure rib pattern may alternatively be octagonal, hexagonal, or the like.

Expanded rigid plastic foam has not been used in the bed foundation industry up to now, and is extremely strong while being relatively light in weight. In an exemplary embodiment of the invention, the foam was selected from the group consisting of phenolic, urethane, and poly-isocyanate rigid foam for its flame retardant properties and physical strength. The material may include other additives such as anti-oxidants, dyes for different color effects, particulate or fibrous fillers for added strength, and mold release agents. A bed foundation unit of this material will be rigid, strong, and light in weight, as well as exhibiting high flame retardant properties which will meet current U.S. federal standards. Another advantage in using expanded rigid plastic foam material for the uni-body foundation is that the material develops a dense, protective skin when molded. This skin has inherent flame resistance and strength that allow for massive cost reductions over conventional plastics when giving equivalent or improved performance.

The box-like enclosure is integrally molded in one piece, for example by reaction injection molding, to form a uni-body foundation. In an exemplary embodiment of the invention, the top panel has a plurality of small air holes extending over its entire area to accommodate airflow through the mattress. These air holes are useful in maintaining freshness of mattress sets within enclosed spaces, by allowing air flow through the units and discouraging development of mold and mildew.

The side and end panels may have openings, recesses or cut-outs of predetermined shape to reduce the amount of material required to manufacture the foundation and reduce overall weight, while still providing a sufficiently strong load-bearing structure. The openings may be of shapes such as elliptical, triangular, square or other shapes which have load-bearing properties, and there may be a single large opening in each panel or several spaced, smaller openings and cavities. Horizontal slots may be provided in one end panel for mounting of a conventional head board.

In an exemplary embodiment of the invention, one or more slide-out drawers may be mounted in a suitable opening in one or more of the side and lower end panels, to provide storage space for bedclothes or the like. Additionally, the outer surfaces of the side and end panels may be textured in order to simulate a quilted cover of the type often found on conventional bed foundation units. A textured surface finish may also be provided on the upper surface of the top panel. This provides a non-skid surface to resist slipping of the mattress from its proper position centered on the foundation.

This arrangement therefore provides a single, open box shape foundation which can replace a previous bed frame and foundation or box spring combination, when plastic legs are inserted in the corner openings. Additional triangular supports with leg openings may be provided in the center of one or more cross slats, if provided, and may be desirable for larger size mattress foundations. The foundation is much simpler, lighter in weight, and less expensive than conventional bed foundations, and will have improved flame retardant properties.

According to another aspect of the present invention, a bed foundation is provided, which comprises a rectangular top panel having opposite sides, opposite ends, and four corners, a pair of side panels depending downwardly from opposite sides of the top panel, and a pair of end panels depending downwardly from opposite ends of the panel to form a box-like enclosure having an open lower end, the panels being of plastic material, at least one of the side or end panels having a rectangular opening, and a drawer slidably mounted in the opening for movement between an open position providing access to the drawer, and a closed position flush with the respective panel.

The foundation is of predetermined dimensions based on the size of the mattress to be supported, and will be provided in different sizes to accommodate single, double, queen, king or other standard bed dimensions. The side and end panels will also be provided in different, standard heights, such as eight inch and nine inch.

The bed foundation of this invention is made substantially or entirely of expanded rigid plastic foam material, which is exceptionally strong yet ultra light in weight. This material also develops a dense skin when molded, which has inherent flame resistance, unlike a conventional bed foundation which includes wood components. The foundation exceeds all proposed and current U.S. flammability standards for beds. The uni-body version requires no assembly tools and can be readily installed. All of the alternative versions are very inexpensive to produce and are of relatively simple construction, and can completely eliminate current metal bed frames and separate box springs.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be better understood from the following detailed description of some exemplary embodiments of the invention, taken in conjunction with the accompanying drawings in which like reference numerals refer to like parts and in which:

FIG. 1 is a perspective view, partially cut away, of an exemplary form of the bed foundation of this invention;

FIG. 2 is an enlarged sectional view taken on line 2-2 of FIG. 1;

FIG. 3 is an end view of the bed foundation showing an alternative arrangement of the lightening cut outs;

FIG. 4 is a side view of the bed foundation with support legs and a mattress or box spring added;

FIG. 5 is a top plan view, partially cut away, of an alternative knock down configuration of the bed foundation;

FIG. 6 is an enlarged view of one corner of the structure of FIG. 5;

FIG. 7 is an enlarged sectional view taken on line 7-7 of FIG. 5;

FIG. 8 is an end view similar to FIG. 3, but showing means for attachment of the headboard;

FIG. 9 is a sectional view taken on line 9-9 of FIG. 8, with a headboard secured in place;

FIG. 10 is a top plan view of a box spring base unit according to another embodiment of the invention.

FIG. 11 is an enlarged sectional view taken on line 11 of FIG. 10, with box springs and a cover indicated in broken line;

FIG. 12 is a side view of one end of the base of FIG. 10 with a headboard attached;

FIG. 13 is a bottom perspective view of a bed foundation according to another embodiment of the invention;

FIG. 14 is a top perspective view of one of the drawers for sliding engagement in a side opening in the foundation of FIG. 13;

FIG. 15 is a top perspective view of the foundation of FIG. 13, with the drawers in place;

FIG. 16 is a cross sectional view on the lines 16-16 of FIG. 14;

FIG. 17 is a cross sectional view on the lines 17-17 of FIG. 13, with a drawer in place in the drawer support;

FIG. 18 is perspective view of a leg for engaging in a leg mounting bore in the foundation.

FIG. 19 is a perspective view similar to FIG. 14 illustrating the foundation supported on legs mounted in the respective mounting bores.

FIG. 20 is a bottom perspective view of a bed foundation according to another embodiment of the invention; and

FIG. 21 is a top perspective view of the foundation of FIG. 20.

DETAILED DESCRIPTION OF THE DRAWINGS

FIGS. 1 to 4 of the drawings illustrate a uni-body bed foundation unit 10 according to a first embodiment of the present invention, for supporting box spring and mattress, or a mattress 12 placed directly on top of unit 10 as indicated in FIG. 4. It will be understood that the unit will be made in a range of lengths and widths corresponding to the various standard mattress sizes, such as single or twin, full, queen, king, California king, and in both standard lengths and extra long lengths.

The unit 10 of FIGS. 1 and 2 is molded in one piece from an expanded rigid plastic foam material. This material is cold-poured into a suitably shaped mechanical mold. Expanded rigid plastic foam materials are extremely lightweight yet durable, strong, and flame retardant. In an exemplary embodiment the material was selected from the group consisting of phenolic, urethane and poly-isocyanate rigid foam of the closed cell variety, for flame retardancy, and may be of a rating (cell density) of 90% or more.

Unit 10 has a rectangular upper panel 14 which has a continuous, flat upper surface 15 for supporting a mattress 12 as in FIG. 4, or a conventional box spring with a mattress placed on top, if desired. Integral side walls 16 and end walls 18 depend downwardly from the opposite side edges and end edges of panel 14. This forms a box-like structure with a lower end opening. One or more integral cross slats 20 may extend between the opposite side walls 16 if required for additional strength. The unit also has integral, triangular corner blocks or bosses 22 at the four corners of the box-like structure. A mounting bore 24 extends upwardly from the lower face of each corner block 22, for receiving the end of a support leg 25 of the same material as unit 10. Support legs 25 are a press fit in the respective mounting bores.

For larger size mattresses, and thus larger size foundation units 10, one or more additional support legs may be provided along the sides and at the center of the or each cross slat 20, for example. In this case, triangular supports with leg mounting bores will be formed integrally at the center of a cross slat and/or at the junctions between cross slats and side walls. As noted above, a mattress may be placed directly on top of foundation unit 10, as indicated in FIG. 4, so that the unit replaces both a conventional metal bed frame and a conventional wood and metal box spring normally placed on a metal bed frame to provide a flexible support for the mattress. In this case, a non-flexible support surface for the mattress is provided. However, a flexible surface laminate 27 of the same material as unit 10 but lower density may be provided on top of the less flexible panel 14, as indicated in dotted outline in FIG. 2, to provide a support surface with a flexible yield, simulating a box spring structure. This provides a dual durometer layer construction for panel 14, comprising a lower layer of higher rigidity and an upper layer of higher flexibility. The two layers may be of substantially equal thickness or of different thicknesses.

Each side wall 16, end wall 18, and cross slat 20 (if present) has one or more openings or cut outs. In the embodiment illustrated in FIGS. 1 and 2, each side wall has two rectangular openings 26 and each end wall and cross slat has one rectangular opening 28 extending across the majority of its length. These openings have the purpose of reducing the amount of material required, and thus the overall weight and cost of the foundation unit, while not significantly reducing strength. Although the openings are relatively large, rectangular openings in this embodiment, they may be of other shapes and dimensions, such as a plurality of circular openings 30 as illustrated in FIG. 3, or of elliptical, square, polygonal, triangular, irregular or other shapes, or combinations of different shape openings. The overall effect is removal of 50% or more of the total material required for making a solid wall of corresponding dimensions having no openings.

As discussed above, foundation unit 10 may be manufactured by cold-pouring the selected expanded rigid plastic foam material into a mold with corresponding side wall openings and surface structure. This technique generates no scrap or trimming waste and is extremely efficient. Uni-body molding therefore allows the use of less material and produces an inherently strong, integral box-like structure. However, shipping costs may be relatively high due to the overall size of the units.

FIGS. 5 to 7 illustrate an alternative, knock-down mattress foundation unit or foundation assembly 35. This unit is of similar structure to the one-piece or uni-body unit 10, but is made in several separate generally flat parts which can be secured together by suitable fasteners such as screws 36. The parts comprise at least a flat upper panel 38, a pair of side walls 40, a pair of end walls 42, and four corner blocks or bosses 44 forming both the corner and the leg mounting boss at each corner of the unit 35. For larger size mattresses, the knock-down unit also comprises one or more cross slats 46, and optionally one or more separate, triangular leg mounting units or bosses 48. The side walls, end walls, and cross slat (if present) will all have openings or cut-outs of any desired shape or combination of shapes, such as rectangular cut-outs 26,28 as illustrated in the first embodiment. This will reduce the overall weight of the assembly.

Each part of the foundation assembly 35 is made of the same expanded rigid plastic foam material as the uni-body foundation unit 10 of the previous embodiment. However, since each part other than the corner pieces or leg mounting bosses is a flat panel, no mold is required and the parts may be simply cut from a bun to the appropriate dimensions. The material should be of a higher density, suitably not less than 12 pounds per cubic foot, to enable fastening of the parts with screws 36 and/or adhesives. The thickness of the side and end panels will also be greater in this embodiment than the uni-body version, to provide an adequate anchor for the fasteners. The corner pieces will be molded in a suitable mechanical mold of corresponding shape and dimensions.

As best illustrated in FIG. 6, each corner block 44 is generally triangular in shape, with a rounded outer corner 50, a flat, slanted inner face 52, and cut-outs or recesses 54 on each side for receiving the end of the respective end wall 42 and side wall 40. A leg mounting bore 55 extends upwardly from the lower face of each block 44 for receiving legs 25 in exactly the same manner as illustrated in the first embodiment. When the walls 40,42 are properly engaged in the respective recesses 54, they are secured in position with fastener screws 36 as indicated. These may be Phillips head tec screws or equivalent fasteners. Alternatively, or additionally, spray adhesives may be used to secure the parts together. The upper panel 38 is also secured to the side walls by similar fasteners (not illustrated). The central leg mounting block 48 is a simple triangular block which also has a leg mounting bore 55 and is secured to the cross slat 46 by a screw and/or adhesive.

The advantage of the knock down assembly over the uni-body foundation unit 10 of the first embodiment is that shipping costs will be lower, since the parts can be shipped prior to assembly in a relatively small box, and then assembled on site quickly and easily using only basic hand tools. Once assembled, the joint lines in the knock down assembly will be nearly invisible, due to the compression fit between the parts. The uni-body construction has the advantage of requiring no assembly on site, but will require larger storage space prior to installation and will be more expensive to ship. In both cases, the product is made entirely or almost entirely of expanded rigid plastic foam material (apart from the fastener screws in the case of the knock down version). This material is extremely strong, offering in excess of five times the strength of comparable wood products, is nearly inflammable, and is very light in weight. The foundation is very inexpensive to produce, and completely eliminates the current unattractive and heavy metal bed frame or bed frame and box spring combination, replacing these parts with a single support unit and legs.

The side and end walls or panels in each of the above embodiments will have at thickness in the range of 0.25 to 2.00 inches, with the side and end walls being thicker in the knock down version to anchor the fasteners. The top panel thickness will be in the range of 0.125 to 2.00 inches, again being thicker in the knock down version. As noted above, the density will also be higher in the knock down version, for the same reason. The height of the side and end walls is at least 1 inch, and may be higher than this if desired, based on the desired overall bed height. The length and width of the top panel will be variable depending on the width and length of the mattress to be supported.

FIGS. 8 and 9 illustrate an optional modification of one end wall 18 or 42 of the foundation unit to allow mounting of a headboard 56. End wall 18 or 42 is provided with two spaced pairs of parallel, horizontal slots 58. The lower end of a headboard 56 is secured to the end wall of the foundation unit via nut and bolt fasteners 59 extending through the slots and aligned openings in the headboard, as illustrated in FIG. 9.

In both of the above embodiments, the foundation unit has the general shape of a rectangular box, open at the bottom, with all four corners radiused to the industry standard. On larger units, typically queen size or larger, one or more transverse cross braces may be used, depending on the sleep surface load requirements. If necessary, longitudinal braces may be installed between the end walls for additional strength. The corner units or bosses have mounting bores for the plastic support legs 25, thus eliminating the need for a separate bed frame and further reducing cost and weight.

FIGS. 10 to 12 illustrate a box spring base unit or panel 60 according to another embodiment of the invention, for replacing a conventional wood slat box spring base as well as the metal frame which would normally support a conventional box spring unit. Unit 60 basically comprises a flat, rectangular panel with radiused corners 62. The lower surface 64 of the panel may have rectangular recesses 65 extending across a major portion of its width, as indicated in FIGS. 10 and 11, to reduce overall weight. This also produces a shape similar to that of a conventional wood slat box spring, with the strips or portions 66 of material between the recesses corresponding in position to the conventional wood slat. The recesses may be replaced with openings extending through the entire thickness of the panel, if desired. However, a solid panel will exhibit better flame retardancy.

The panel or unit 60 will be made of the same expanded rigid plastic foam material as the foundation units of the previous embodiments, and may be made by cutting a bun slice of the foam material of the appropriate thickness, or by molding. The foam material selected may have a density of the order of fifteen pounds per cubic foot. Downwardly facing leg mounting bores 68 are provided at each corner for receiving the end of plastic support legs 25, avoiding the need for a separate metal bed frame.

In order to complete the box spring unit, metal box springs 70 are tacked onto the upper surface 72 of the panel, as illustrated in FIG. 11, and a suitable cover 74 is placed over the box springs. The springs may be attached only around the periphery of the recesses and along the strips 66 between adjacent recesses, if desired. A mattress may then be placed on top of cover 74. A solid panel with no openings has the advantage of higher flame retardancy, since it will prevent flames from beneath the bed from penetrating to the burnable materials typically used to enclose the box springs.

FIG. 12 illustrates a headboard mounting bracket 75 for use with the box spring flat or unit 60. Bracket 75 has a channel or groove 76 for engaging over an end of the panel or unit 60. Bracket 75 is secured to the panel 60 via bolts 77, and has an upright mounting flange 80 for attachment to the lower end of the headboard 56 via bolts 82 which extend through a slot in flange 80. The bracket 75 may be made of the same lightweight and flame retardant foam material as the box spring flat 60.

The panel 60 may have a thickness of the order of 0.125 to 2.00 inches to provide adequate supporting strength for the box spring and mattress. The cross brace width, or width of portions 66 between adjacent recesses or openings, should be at least six inches to provide an adequate base for the attached row of springs.

FIGS. 13 to 19 illustrate a bed foundation 100 according to another embodiment of the invention. The foundation is molded in one piece from an expanded rigid plastic foam material, apart from the drawers 102 and drawer support structures 118, 119 which are molded separately. In one exemplary embodiment, the foam material was a polyurethane rigid foam comprising a polyol, an isocyanate, and optional additives such as anti-oxidants and mold release agents. The foundation may be fabricated in one piece by reaction injection molding, producing a unitary foundation with no seams or joints.

The expanded rigid plastic foam material used to mold the foundation has the property that a dense skin 101 is formed when it is molded. This outer skin has inherent flame resistance and strength when compared to conventional plastics materials. The production of a protective, flame retardant skin on a bed foundation is extremely advantageous in meeting flammability standards. The foam material may include particulate or fibrous fillers added to the resin, creating a composite material. Any basic plastic composite fillers may be used, including silica and boric oxide. Layers of fiberglass matting may be incorporated in the foundation walls in lieu of, or in combination with, the fillers as a structural enhancement. The matting may simply be laid in the mold prior to blowing in the polyurethane foam material around and over it. The use of fillers will enhance the structural strength of the foundation unit while decreasing material costs, since less polyurethane will be needed. The range of fiber material in the mixture may be from 1% to 49% by eight, depending on formulation and filler type.

The foundation is illustrated in FIGS. 13 to 19 with optional slide-in drawer support structures 118, 119 for supporting drawers 102, as well as leg adapters 104. However, one or both of these options may be eliminated in alternative embodiments where the foundation is to be mounted on a conventional bed frame and/or where no drawers are required.

The foundation 100, as in the first embodiment above, is of generally rectangular box-like shape, having a flat upper panel or support 105 on which a mattress will be supported in use, and integral, downwardly depending side walls 106 and top and bottom end walls 108, 109. However, unlike the first embodiment, the foundation of this embodiment has an integrally formed, lattice support structure comprising perpendicular sets of intersecting longitudinal and transverse ribs 110, 112 on the inner or lower surface of the upper panel 105. Additionally, a plurality of air holes or openings 114 are provided in the upper panel, as best illustrated in FIGS. 13 and 15.

In the illustrated embodiment, one air hole is provided at the center of each rectangular cell 115 formed by the intersecting sets of ribs 110, 112, although a lesser number will be provided in alternative embodiments. The number and size of the air holes 114 selected will be dependent on various factors. The purpose of the air holes is to provide air flow to the mattress and maintain freshness of the mattress, reducing the risk of mold or mildew forming in a potentially damp environment. A secondary purpose is to reduce the overall weight of the foundation. Typically, the air holes will be larger where more air flow is required, for example in smaller rooms or more enclosed environments.

A series of five leg adapters 104 are also molded into the interior of the foundation, one at each corner of the foundation and one at the center of the foundation, as best illustrated in FIG. 13. Each leg adapter 104 comprises a hollow post of generally square cross section. Legs 116 are provided for press fitting into the respective adapter bores if the foundation is to be used without a conventional metal bed frame, as illustrated in FIGS. 19 and 20. However, the leg adapters 104 may be eliminated if this option is not desired. As best illustrated in FIG. 19, each leg 116 has a tapering portion 117 of square cross section which is a frictional or interference fit into a respective bore 104, and a shaped lower end portion 119 which acts as the support to hold the foundation above the floor, as illustrated in FIG. 19.

The embodiment of the foundation illustrated in FIGS. 13 to 19 has two slide-in drawer units 102, one in each side wall 106. A rectangular drawer support structure comprising a pair of side walls 118 and an end wall 120 is secured in each side of the foundation in alignment with a respective drawer opening 124. Each side wall 118 of the drawer support has a slide groove 122 as best illustrated in FIG. 17. Each drawer unit 102 has a slide rib 125 on each side for sliding engagement in the respective groove 122 and an outer face 126 which fits into opening 124 when the drawer is closed, as illustrated in FIG. 15.

In the embodiment of FIGS. 13 to 19, the outer side and end faces of the foundation, and the outer faces 126 of each drawer, if provided, have a textured pattern 128 of wavy lines, as best illustrated in FIGS. 13, 15 and 17. The textured pattern may be formed in the mold. Where the foundation has drawers, the textured pattern on the outer faces 126 is designed as a smooth continuation of the pattern on adjacent regions of the side walls, as seen in FIG. 15. This may be done by initially forming the side walls with textured pattern, then cutting out a portion of each side wall to form drawer opening 124, and using the cut out portion as the outer face 126 of the drawer unit.

The textured pattern is provided on the outer surfaces of the foundation which will be visible when the foundation is in use, and is designed to simulate the quilting pattern of a more conventional foundation with a traditional fabric cover. The textured surface of the side and end walls may be of any desired quilting pattern, such as lockstitch, chain stitch and “tack and jump” patterns as known in the field, or may be of other decorative patterns if desired. The upper surface of the upper wall 105 of the foundation may also be provided with a slightly roughened texture by suitable roughening or sand blasting of the corresponding mold surface. This will produce a non-skid surface, reducing the risk of a mattress slipping to one side in use.

The lattice support structure of longitudinal and transverse ribs or stringers 110, 112 provides a support system for the upper wall or horizontal platform 105, and also adjusts the level of support provided for the mattress. The rib height and thickness can be modified for increased or reduced support, as necessary. In the illustrated embodiment, the longitudinal ribs 110 are of fixed height while the transverse ribs 112 vary in height from the ends to the center of the foundation, as illustrated in FIG. 13, with the ribs 112 being taller at the center of the foundation where more support is typically required. The ribs 110, 112 have tapered extensions 130 at their ends extending towards the open bottom end of the foundation, at the junction between the upper wall or panel 105 and the side and end walls, to provide the necessary edge support, as best seen in FIG. 13. Although the ribs are perpendicular in the illustrated embodiment and form a rectangular lattice pattern, the lattice support structure may alternatively be formed in a diamond, hexagonal, octagonal, or other regular pattern.

Although the foundation unit in FIGS. 13 to 19 is provided with two slide-out drawers in the side walls, additional drawers may be provided if desired, as space permits, for example in the end wall 109, and the drawers and drawer supports may be omitted altogether in other alternative embodiments. The top end wall 108 of the foundation unit 100 may be modified to allow for mounting of a headboard, in the same way as illustrated in FIGS. 8 and 9 for the first embodiment. If desired, the side and bottom end walls may also be provided with cut outs, as in the first embodiment, to reduce material costs and overall weight of the unit.

FIGS. 20 and 21 illustrate a modified foundation unit 150 which is similar to the foundation unit of the previous embodiment, but which is of simpler structure. As in the previous embodiment, foundation unit 150 has an upper wall or panel 152 and downwardly depending side walls 154 and end walls 155, as well as an integrally formed lattice support structure on the lower surface of the upper panel 152. The lattice support structure comprises two sets of parallel, intersecting longitudinal and transverse ribs or stringers 156, 158. As in the previous embodiment, the transverse ribs 156 are of gradually increasing height from each end wall 155 up to the center of the foundation, where they have a maximum height for added support and strength in this region.

The outer surfaces of the side and end walls in this embodiment are smooth and have no textured pattern, unlike the previous embodiment. The foundation of FIGS. 20 and 21 may be provided with a conventional fabric foundation cover. The lower edges of the side and end walls may be curved inwardly to provide a convenient staple lip for attachment of the cover. There are also no drawer openings or supports, or drawers, and no leg adapters, although leg adapters 104 may optionally be provided in this version. As in the previous embodiment, a series of air holes 160 are provided in the upper wall 152 for air flow to the mattress. The air holes 160 are smaller in this case, and are of the order of 0.5 inches in diameter. This size of air hole will be used where there will be plenty of space and ventilation in the room where the foundation will be used. Again, airflow is provided through the foundation to the mattress, thereby discouraging the formation of mold and mildew. The air hole diameter will be increased for foundations to be used in more enclosed spaces.

In each of the above embodiments, a conventional metal bed frame and foundation or box unit or box spring is replaced by a simple, lightweight unit or assembly of flame retardant, expanded rigid plastic foam material. In the first two embodiments and the last two embodiments, the foundation is of a box-like shape with an open base, and the mattress is placed directly on top of the upper panel of the unit. In the third embodiment, the foundation is a flat panel for replacing a conventional box spring base or flat, with corner openings for receiving plastic legs, and with box springs stapled to the upper surface of the panel with a suitable surrounding enclosure. The material chosen for the bed foundation of this invention is a considerable improvement over conventional bed frame and foundation construction materials, with much higher flame retardancy, lighter weight, reduced complexity, yet equivalent or better strength and durability. This invention completely eliminates the need for a separate metal bed frame when used with the leg adapters and optional plastic legs.

Molding of the foundation unit in rigid plastic foam material such as a polyurethane rigid foam will inherently produce an outer protective skin which has flame retardant properties, unlike conventional plastic materials as previously used in bed products. The air flow holes in the upper panel can be customized for the environment in which the foundation will be used, and will help to maintain the freshness of the mattress and reduce formation of mold and mildew. The optional texturing of the side and end walls of the unit can simulate the effect of a conventional fabric foundation cover at reduced expense.

Although some exemplary embodiments of the invention have been described above by way of example only, it will be understood by those skilled in the field that modifications may be made to the disclosed embodiments without departing from the scope of the invention, which is defined by the appended claims. 

1. A bed foundation, comprising: a rectangular top panel having opposite sides, opposite ends, and four corners, a pair of side panels depending downwardly from opposite sides of the top panel, and a pair of end panels depending downwardly from opposite ends of the panel; the panels being formed integrally to form a unitary box-like enclosure having an open lower end, and being of expanded rigid plastic foam material; the top panel having an upper surface and a lower surface; and a support structure formed integrally on the lower surface of the top panel, the support structure comprising raised ribs forming a predetermined regular pattern.
 2. The foundation as claimed in claim 1, wherein the support structure comprises first and second sets of parallel ribs which intersect at an angle to one another to form a lattice.
 3. The foundation as claimed in claim 1, wherein some of the ribs are thicker than others.
 4. The foundation as claimed in claim 2, wherein the lattice has a rectangular pattern.
 5. The foundation as claimed in claim 3, wherein the lattice has a triangular pattern.
 6. The foundation as claimed in claim 1, wherein the support structure has a hexagonal pattern.
 7. The foundation as claimed in claim 1, wherein the support structure has an octagonal pattern.
 8. The foundation as claimed in claim 1, wherein the foam is selected from the group consisting of phenolic, urethane, and poly-isocyanate rigid foam.
 9. The foundation as claimed in claim 8, wherein the foam contains at least one additive selected from the group consisting of anti-oxidants, dyes, and mold release agents.
 10. The foundation as claimed in claim 1, wherein the top panel has a plurality of air holes extending over its entire area for providing airflow to a mattress supported on the foundation.
 11. The foundation as claimed in claim 10, wherein each air hole has a diameter in the range from 0.5 inches to 4 inches.
 12. The foundation as claimed in claim 1, wherein at least one of the side and end panels has an opening, and a drawer is slidably mounted in the opening for movement between open and closed positions.
 13. The foundation as claimed in claim 1, wherein the side and end panels have outer surfaces which are textured to produce a predetermined pattern.
 14. The foundation as claimed in claim 13, wherein the pattern simulates a quilted pattern.
 15. The foundation as claimed in claim 1, wherein the top panel has a textured, slip resistant upper surface.
 16. The foundation as claimed in claim 1, further comprising a leg adapter at each corner of the enclosure, each leg adapter having a lower open end and a bore extending upwardly from the lower open end for receiving the end of a support leg for supporting the enclosure at a position raised above a floor surface.
 17. The foundation as claimed in claim 16, wherein an additional leg adapter is provided at the center of the enclosure.
 18. The foundation as claimed in claim 16, wherein each leg adapter comprises a hollow post of square cross-section extending from the upper panel to the open lower end of the enclosure.
 19. The foundation as claimed in claim 1, wherein the side panels each have at least one opening.
 20. The foundation as claimed in claim 19, wherein the openings are rectangular.
 21. The foundation as claimed in claim 20, including two drawer units, each drawer unit being adapted for releasable slidable engagement through the opening in a respective side panel.
 22. The foundation as claimed in claim 19, wherein the openings are circular.
 23. The foundation as claimed in claim 19, wherein the openings extend over at least 50% of the total surface area of the respective panel.
 24. The foundation as claimed in claim 1, wherein one end panel has horizontal slots for mounting of a head board.
 25. The foundation as claimed in claim 1, wherein the foam is of the closed cell variety.
 26. The foundation as claimed in claim 1, wherein the foam has a density in the range from 5 to 20 pounds per cubic foot.
 27. The foundation as claimed in claim 2, wherein the two sets of ribs comprise a first set of spaced longitudinal ribs extending between the opposite end panels and a second set of spaced transverse ribs extending between the opposite side walls.
 28. The foundation as claimed in claim 27, wherein at least the transverse ribs are of varying height, the transverse ribs having a height which increases from a minimum height at the end wall to a maximum height at the center of the enclosure.
 29. The foundation as claimed in claim 27, wherein each rib has opposite ends at a junction with the respective opposite side or end panels of the enclosure, each end having an extension extending towards the open end of the enclosure for providing edge support to the foundation.
 30. The foundation as claimed in claim 1, wherein the foam material is a composite material containing a filler material which is s elected from the group consisting of particulate and fibrous fillers for plastic composite materials.
 31. The foundation as claimed in claim 30, wherein the filler material is in the range from 1% by weight to 49% by weight.
 32. A bed foundation, comprising: the top panel, and a pair of end panels depending downwardly from opposite ends of the panel to form a box-like enclosure having an open lower end, the panels being of plastic material; at least one of the side or end panels having an opening; and a drawer slidably mounted in the opening for movement between an open position providing access to the drawer, and a closed position flush with the respective panel.
 33. The foundation as claimed in claim 32, wherein the box like enclosure and drawer are formed of expanded rigid plastic foam material.
 34. The foundation as claimed in claim 33, wherein the top panel, side and end panels each have an inner surface, and a lattice support structure comprising first and second sets of intersecting ribs is formed integrally on the inner surface of the support panel and extends up to the inner surfaces of the side and end panels.
 35. The foundation as claimed in claim 32, wherein the top panel has a plurality of air holes extending over its entire surface.
 36. A bed foundation, comprising: a rectangular top panel having opposite sides and opposite ends; a pair of side panels and a pair of end panels depending downwardly from the sides and ends of the top panel, respectively, to form a box-like enclosure having an open lower end; the top panel, side panels, and end panels being molded integrally in one piece from expanded rigid plastic foam material; and the top panel having a plurality of openings. 